Earth boring machine with a readily replaceable drill rod chuck

ABSTRACT

Rotary, compressive and tensile forces are transmitted through a replaceable chuck to a rotary drill string to bore a large diameter hole by initially drilling a small diameter hole and subsequently enlarging the small diameter hole into the desired large diameter hole with a reaming operation. The drill string is rotated with rotary drilling equipment mounted upon a movable carriage. The uppermost drill rod of the drill string is connected to the main drive spindle of the rotary drilling equipment by the replaceable chuck. A pair of cap screws and a clamp ring allow the replaceable chuck to be easily and quickly removed from the main drive spindle. Rotary force from the main drive spindle is transmitted to the replaceable chuck by a square recess on the main drive spindle that mates with a raised square on the replaceable chuck. The replaceable chuck is provided with an axial floating action for make up and break out of the threaded connection between the drill stem and the replaceable chuck. A register pilot on the replaceable chuck mates with a pilot recess on the main drive spindle to provide alignment.

United States Patent 1 1 7 1111 3,744,577

Williams 1 July 10, 1973 l EARTH BORING MACHINE WITH A [57] ABSTRACTREADILY REPLACEABLE DRILL ROD Rotary, compressive and tensile forces aretransmitted CHUCK through a replaceable chuck to a rotary drill/stringto [75 Inventor: Raymond Leroy Williams, bore a large diameter hole byinitially drilling a small Beaumont, diameter hole and subsequentlyenlarging the small diameter hole into the desired large diameter holewith Asslgneel Dreiser Industries, u Dallas, a reaming operation. Thedrill string is rotated with rotary drilling equipment mounted upon amovable car- [22] Flled' 1971 riage. The uppermost drill rod of thedrill string is conl l PP N05 185,603 nected to the main drive spindleof the rotary drilling equipment by the replaceable chuck. A pair of cap52 Us. (:1 173/163, 64/1, 175/170, Screws and a Clamp ring allow thereplaceable chuck 287/130 be easily and quickly removed from the maindrive 511 1m. (:1 E2lb 17/046 spindle- Rmary fmce the main drive Spindleis 58 Field of Search 173/163, 164, 152-158; transmitted replaceablechuck by a Square recess 175/52 5 122 170. 4/1. 2 7/111 113 130 on themain drive spindle that mates With a raised square on the replaceablechuck. The replaceable l 56] References Cited chuck is provided with anaxial floating action for make up and break out of the threadedconnection between 3 343 612 I J PATENTS 173" the drill stern and thereplaceable chuck. A register owers 1 p1lot on the replaceable chuckmates with a p1lot recess ii on the main drive spindle to providealignment. 3:463:24? 8/1969 Klein 175/85 x Primary Examiner-Ernest R.Purser 18 Claims, 5 Drawing Figures A ttdrney-Robert W. Mayer, Eddie E.Scott et al.

PATENIEUJUL 1 mm SHEU 1 0F 2 FIG. 3

FIG. I

INVENTORI RAYMOND L. WILLIAMS FIG. 2

ATTORNEY PATENTEB 1 01975 SHEET 2 [If 2 FIG. 4

' INVENTORY RAYMOND .L. W/LLIAM$ ATTORNEY BACKGROUND OF THE INVENTIONThe present invention relates to the art of earth boring and moreparticularly to a drill rod chuck that may be easily and quicklyreplaced and will withstand large axial and torque loads.

This invention has special utility in a raise drilling system whereinthe raise hole boring operation proceeds by the drilling of a relativelysmall pilot hole followed by enlargement of the pilot hole to thedesired size. Raise drilling operations require a wide range of drillingspeeds and torques. For example, when drilling the pilot hole, a smalldiameter bit is used and rotated at high speed with low torque. When thepilot hole is being enlarged into the large diameter raise hole, a muchlarger bit is connected to the drill string and the drill string isrotated at slow speed with high torque. The pilot hole drillingoperation places a compressive axial load upon the drill string and theraise operation wherein the pilot hole is being enlarged into a largediameter hole places a tensile load upon the drill string.

It will therefore be appreciated that the chuck used to connect thedrill string to the rotary drilling equipment must be strong and durableto withstand the wide variety of loads imposed upon it. In addition, theconnection between the drill string and the rotary drilling equipmentmust be failure proof to insure that the large diameter raise bit andthe drill string will not be dropped when enlarging the pilot hole intoa large diameter hole. The dropping of the large diameter bit and thedrill string would not only result in damage to the equipment but wouldcreate a serious safety hazard. The large diameter bit and the drillstring falling downward through the portion of the large diameter holethat has already been bored travels with a great amount of force and anypersonnel working below would be in danger.

The threads of the chuck that connect the uppermost drill rod of thedrill string to the rotary drilling equipment may become worn or damagedduring the drilling operation through the repeated make up and break outof the drill string. As previously explained, the high loads imposedupon the chuck during the drilling operation and the dangers involved indropping the drill string are great and any weakness in the system mustbe avoided. Therefore, once the threads in the chuck become worn ordamaged, the chuck must be replaced. Because of the large expenseinvolved in this type of a drilling operation, the time the equipment isnot drilling must be kept to a minimum. It is therefore important that aremovable chuck be-provided that is easily and quickly replaceable. Whenproviding a replaceable chuck, it is desirable to provide a chuck thathas few intricate parts that require time-consuming adjustments andhandling. In addition, the chuck is subjected to corrosive forces duringthe drilling operation such as dust that accumulates in the workingparts and drilling fluid that contacts the working parts. The rotarydrilling equipment is generally positioned in the confines of a mine andthe chuck must be adaptable to being changed with a limited amount ofaccess and without requiring the use of large tools.

It is also highly desirable to be able to reduce the ex penses involvedin manufacturing the drilling equipment. This means that the elements ofthe equipment should be of a simple design and adaptable to beingmanufactured according to less expensive manufacturing operations. Thisis particularly true for a replaceable element of the drilling equipmentsuch as the replaceable chuck. The chuck is only used until it becomesworn or damaged. It is then replaced by a new chuck and the drillingoperation continued.

DESCRIPTION OF THE PRIOR ART A general summary of raise drilling isprovided in U.S. Pat. No. 3,220,494 to R. E. Cannon, et al., patentedNov. 30, 1965. A large diameter raise hole is produced between twolevels of a mine by positioning rotary drilling equipment at the upperlevel of the mine and drilling a small pilot hole from the upper levelof the mine to a mine level below. The small diameter pilot bit is thenremoved from the drill string and a large diameter raise cutter head orraise bit attached to the drill string. The pilot hole is enlarged tothe desired size by rotating and hydraulically raising the raise bitalong the pilot hole.

In U. S. Pat. No. 3,463,247 to H. T. Klein, patented Aug. v26, 1969, asystem for connecting a rotary drill string to rotary drilling equipmentand for breaking out the sections of the drill string from the rotarydrilling equipment is shown. This system includes a drive head that isconnected to the rotary drilling equipment. A collar having internalthreads is positioned within the drive head for engaging the threads onthe upper portion of the drill string. The drive head and collar arelocked to the rotary drilling equipment by a series of bolts. A seriesof splines transmit torque from the drive head to the internal collar.

The system shown in the Klein patent has the disadvantage of the boltsand the splines tending to shear during the drilling operation. Sincethe bolts connect two flat surfaces together, the sharp angular edges ofthe surfaces produce a shearing force on the bolts under the high torqueload. The bolts are also subjected to high tensile loads and are subject'to failure. When the large diameter bit is being moved along the pilothole during the raising operation, the bolts are sub jected to both theweight of the entire drill string and the large load that is placed uponthe bit to move it along the pilot hole and ream the pilot hole into alarge diameter hole.

This system also has the disadvantage of the bolts tending to becomeloose during the drilling operation. The bolts must therefore beperiodically tightened and failure to do so may result in the droppingof the drill string.

When it becomes necessary to change the internal collar because thecollar has become'worn or damaged, all of the bolts must be undone andthe head removed. A new collar is inserted and the bolts are replacedand tightened. This requires a considerable amount of time anddifficulty. It can also be appreciated that the corrosive environmentalconditions of the mine may make the loosening and tightening of a largenumber of bolts very difi'icult. The large number of bolts and splinesare also quite expensive to manufacture.

In U. S. Pat. No. 3,490,546 to .l. S. Hattrup, et al., patented Jan. 20,1970, a drilling machine for use in small tunnels is shown. This machineincludes a connector with internal threads that allows the drill stringto be connected to the rotary drilling equipment. The connector has anupper ball portion with an outer spherical v surface that mates with theinner spherical surface on a bell element connected to the main shaft ofthe rotary drilling equipment. A retainer bolts the bell element to theoutput shaft of the rotary drilling equipment and a series of splinesare positioned to transmit rotary torque from the bell to the connector.This system for connecting the drill stem to the rotary drillingequipment of the machine has all of the disadvantages associated withthe connecting system mentioned above.

SUMMARY OF THE INVENTION The present invention provides a replaceablechuck that will eliminate stress failures in connecting a rotary drillstring to rotary drilling equipment. The chuck may easily and quickly beremoved from the rotary drilling equipment and a new chuck attached toreplace a chuck that has become worn or damaged or for inserting a newchuck of a different size to allow the use of drill string components ofvarious sizes. Rotary torque is transmitted from the main drive spindleof the rotary drilling equipment to the chuck by an angular protrusionadapted to mate with a matching angular recess. Axial forces aretransmitted from the main drive spindle to the chuck by a clamp ringpositioned around the spindle and the chuck. The clamp ring is locked inplace by at least one replaceable locking element. A register pilotallows the chuck to be easily positioned in axial alignment with thedrill string and the main drive spindle.

It is therefore an object of the present invention to provide a chuckfor connecting a rotary drill string to rotary drilling equipment thatmay easily and quickly be replaced.

It is a further object of the present invention to provide a chuck forconnecting a rotary drill string to rotary drilling equipment that iseasily aligned with the drill string and the main drive spindle when itis being replaced.

It is a still further object of the present invention to provide a chuckfor connecting a rotary drill string to rotary drilling equipment thatwill eliminate stress failures.

It is a still further object of the present invention to provide a chuckfor connecting a rotary drill string to rotary drilling equipment thatwill transmit high torque loads from the rotary drilling equipment tothe drill string.

It is a still further object of the present invention to provide a chuckfor connecting a rotary drill string to rotary drilling equipment thatwill transmit high tensile loads from the rotary drilling equipment tothe drill string.

It is a still further object of the present invention to provide a chuckfor connecting a rotary drill string to rotary drilling equipment thatwill allow a limited amount of axial movement of the chuck relative tothe rotary drilling equipment.

The above and other objects and advantages of the present invention willbecome apparent from a consideration of the following detaileddescription of the invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in side elevation ofan earth boring machine with a replaceable chuck constructed inaccordance with the present invention connecting a rotary drill stringto the rotary drill equipment of the machine.

FIG. 2 is a sectional view of the replaceable chuck that connects thedrill string to the main drive spindle of the rotary drilling equipment.

FIG. 3 is a top view of the replaceable chuck shown in FIG. 2.

FIG. 4 is a sectional view of another embodiment of the replaceablechuck of the present invention.

FIG. 5 is a top view of the replaceable chuck shown in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings indetail and in particular to FIG. 1, shown therein and generallydesignated by the reference number 10 is an earth boring machine. Therotary drilling equipment of the machine is held in place by a pair ofsupport columns (one column 12 being shown in FIG. 1) pivotally mountedupon a base 14 by a pair of hinges (one hinge 16 being shown in FIG. 1).The supports are held in position by at least one brace 18 which isconnected between the base 14 and the upper portion of the support 12.The brace 18 is attached to the base 14 by a connection 20, and to theupper portion of the support 12 by a connection 22. A means of adjustingthe length of brace 18 is provided consisting of a threaded sleeve 24that is connected with threaded portions of the brace 18. When thesleeve 24 is rotated in one direction the length of the brace 18 will beshortened and when the sleeve 24 is rotated in the other direction, thelength of the brace 18 will be extended. A movable carriage 26 ispositioned between the pair of support columns and adapted to travelalong the support columns. A main thrust cylinder 28 is connected to themovable carriage 26 and has a piston rod connected to the base member 14by a hinge. The rotary drilling equipment consisting of a power assembly30 and a transmission 32 are mounted upon the movable carriage 26.Actuation of the main thrust cylinder 28 causes the carriage and theassociated rotary drilling equipment to move either up or down along thesupport columns.

When drilling a large diameter hole, the earth boring machine 10 ispositioned at one level in a mine. The uppermost drill rod of a rotarydrill string 34 is connected to the rotary drilling equipment by a chuck36. A small diameter pilot bit connected to the drill string 34 isrotated by the power assembly 30 through transmission 32, chuck 36 anddrill string 34. Axial force is applied to the drill string by thethrust cylinder 28 and the pilot bit is rotated and moved downward toform a small diameter pilot hole. When the thrust cylinder 28 reachesits lowest position, a new drill rod must be added to the drill string.This may be accomplished according to the system shown in U. S. Pat. No.3,446,284 to N. D. Dyer, et al., patented May 27, I969. The drill string34 is disengaged from the chuck 36 and an additional drill rod ispositioned between the chuck 36 and the drill string 34. The upperthreads of the new drill rod are engaged with the threads on the chuck36 and the lower threads of the new drill rod are engaged with the drillstring 34.

Referring now to FIG. 2, the chuck 36 is shown in greater detail. Thechuck 36 consists of a lower portion having internal threads 38 adaptedto mate with the external threads 40 on the uppermost drill rod of thedrill string 34. The upper portion of the chuck 36 includes a raisedcylindrical register pilot 42 that protrudes upward and is adapted tomate with a cylindrical pilot recess 44 in the main drive spindle 46 ofthe earth boring machine 10. A somewhat larger driving square 48protrudes upward from the upper portion of the chuck 36 and is adaptedto mate with a square driving recess 50 in the main drive spindle 46 ofthe earth boring machine 10. Rotary torque is transmitted from the maindrive spindle 46 to the chuck by the driving square 48 and the matchingsquare driving recess 50. The rotary torque of course is thentransmitted to the drill string 34 through the matching threads 38 and40. The register pilot 42 provides centering and axial alignment betweenthe main drive spindle 46 and the chuck 36 when the chuck 36 is beingmounted upon the main drive spindle 46. A central passage 51 allowsdrilling fluid to be pumped through the main drive spindle 46, the chuck36 and the drill string 34.

Tensile force is transmitted from the main drive spindle 46 to the chuck36 by a clamp ring 52 having an upper flange 54 and a lower flange 56.The upper flange 54 fits into a groove 58 on the main drive spindle 46,and the lower flange 56 fits into a groove 60 on the chuck 36. The clampring 52 thereby transmits the axial load from the main drive spindle 46to the chuck 36 and the axial load is then transmitted to the drillstring 34 by the matching threads 38 and 40.

A top view of the chuck 36 and clamp ring 52 is shown in FIG. 3. Theclamp ring 52 is divided into two separate semi-circular clamp ringsections 52' and 52". The two clamp ring sections 52' and 52" areconnected by a pair of cap screws 62 and 62. It is therefore verysimplevto remove the chuck 36 by loosening the cap screws 62 and 62thereby allowing the two sections 52 and 52" of the clamp ring 52 to bewithdrawn from the grooves 58 and 60. A new chuck is positioned belowspindle 46 and the register pilot 42 moved into the pilot recess 44.This provides alignment of the new chuck and the main drive spindle 46.The new chuck can then be turned until the driving square on the newchuck moves into the square driving recess 50. The two sections 52' and52" of the clamp ring 52 are again inserted into the groove on the newchuck and the groove 58 on the main drive spindle 46. The cap screws 62and 62 are tightened to draw the two sections ofthe clamp ring togetherinsuring a firm connection between the main drive spindle 46 and the newchuck.

Referring now to FIG. 4, another embodiment of the replaceable chuck ofthe present invention is shown. The chuck 64 in this embodiment consistsof a lower portion having internal threads 66 adapted to mate theexternal threads 68 on a drill string 70. The upper portion of the chuck64 includes a raised cylindrical register pilot 72 that protrudes upwardand is adapted to mate with a cylindrical pilot recess 74 in the maindrive spindle 76 of an earth boring machine. The somewhat larger drivingsquare 78 protrudes upward from the upper portion of the chuck 64 and isadapted to mate with a square driving recess 80 in the main drivespindle 76 of the earth boring machine. The chuck 64 and the main drivespindle 76 do not abut against one another and a space is maintained toprovide a limited amount of axial movement of the chuck 64 relative tothe main drive spindle 76. This limited amount of axial movement of thechuck facilitates the make up and break out of the drill rod andprevents the internal threads 66 of the chuck 64 from becoming damaged.

Rotary torque is transmitted from the main drive spindle 76 to the chuck64 by the driving square 78 and the matching square driving recess 80.The rotary torque, of course, is then transmitted to the drill stringthrough the matching threads 66 and 68. The register pilot 72 providescentering and axial alignment between the main drive spindle 76 and thechuck 64 when the chuck64 is being mounted upon the main drive spindle76. A central passage 82 allows drilling fluid to be pumped through themain drive spindle 76, the chuck 64 and the drill string 70.

Tensile force is transmitted from the main drive spindle 76 to the chuck64 by a clamp ring 84 having an upper flange 86 and a lower flange 88.The upper flange 86 fits into a groove 90 on the main drive spindle 76and the lower flange 86 fits into a groove 92 on the chuck 64. The clampring 84 therefore transmits the axial load from the main drive spindle76 to the chuck 64 and the axial load is then transmitted to the drillstring 70 by the matching threads 66 and 68.

A top view of the chuck 64 and clamp ring 84 is shown in FIG. 5. Theclamp ring 84 is divided into two separate semicircular clamp ringsections 84' and The two clamp rings sections 84' and 84" are connectedby a hinge 94. This allows the two clamp ring sections 84' and 84" to bepivoted away from each other about hinge 94 and removed from the grooves86 and 92. A cap screw 96 is provided to lock the two clamp ringsections 84' and 84" together once they have been positioned around thechuck 84 and spindle 76. It is therefore very simple to remove chuck 64by loosening the cap screw 96 thereby allowing the two sections 84' and84" of the clamp ring 84 to be separated and withdrawn from the groovesand 92. A new chuck is positioned below spindle 76 and the registerpilot 72 moved into the pilot recess 74. This provides alignment of thenew chuck and the main drive spindle 76. The new chuck can then beturned until the driving square 78 moves into the square driving recess80. The two sections 84' and 84" of the clamp ring 84 are again insertedinto the grooves 90 and 92 and closed about the chuck 64 and the maindrive spindle 76. The cap screw 96 is inserted to connect the sectionsof the clamp ring together. Rotary torque is transmitted from the maindrive spindle 76 to the chuck 64 and at the same time a limited amountof axial movement of the chuck 64 relative to the main spindle 76 isprovided.

The embodiments of the invention in which an exclusive propertyorprivilege is claimed are defined as fol-' lows:

1. An apparatus for transmitting; rotary, compressive and tensile forcesto a drill string to drill a large diameter hole,'comprising:

rotary drilling equipment including a main drive spindle, a motor forrotating said main drive spindle and means for moving said drive spindleaxially;

first angular means on said drive spindle for transmitting rotary force,said first angular means being a driving square recess in the main drivespindle;

a repleaceable chuck including a connection for attaching the drillstring;

second angular means on said replaceable chuck that cooperate with saidfirst angular means for transmitting rotary force, said second angularmeans being a driving square protruding from the replaceable chuck; and,clamp means connected to the replaceable chuck and the main drivespindle for transmitting compressive and tensile forces.

2. The apparatus of claim 1 including alignment means for providingalignment between the replaceable chuck and the main drive spindle.

3. The apparatus of claim 2 wherein said alignment means includes aregister pilot extending from the replaceable chuck and a pilot recessin the main drive spindle.

4. The apparatus of claim 3 wherein said connection for attaching thedrill string includes a set of threads on the rotary drill string and amatching set of threads on the replaceable chuck.

5. The apparatus of claim 4. wherein said set of threads on the rotarydrill string is an external set of threads and the set of threads on thereplaceable chuck is an internal set of threads.

6. The apparatus of claim 5 wherein said clamp means is a clamp ringwith a pair of flanges that engage the main drive spindle and thereplaceable chuck respectively.

7. The apparatus of claim 6. wherein the clamp ring is divided into twosemicircular ring elements that are connected by a pair of screws.

8. The apparatus of claim 6. wherein said clamp ring consists of a pairof semicircular portions connected by a hinge and a lock means.

9. The apparatus of claim 6. including floating means for allowing saidreplaceable chuck to float linearly relative to said main drive spindle.

10. An earth boring maching for drilling by the transmission of rotaryand linear forces to a rotary drill string, comprising:

rotary drilling equipment including a main drive spindle with firstangular means for transmitting rotary forces, said first angular meansbeing a driving square recess in the main drive spindle;

a replaceable chuck with means for connecting the rotary drill string,said replaceable chuck having second angular means for transmittingrotary force that cooperate with said first angular means to transmitrotary force from said rotary drilling equipment to the drill string,said second angular means being a driving square protruding from thereplaceable chuck; and,

clamp ring means connected to the replaceable chuck and the main drivespindle for transmitting linear force between the rotary drillingequipment and the drill string.

11. The earth boring machine of claim 10 wherein said means forconnecting the rotary drill string to the rotary drilling equipmentincludes a set of threads on the rotary drill string and a matching setof threads on the replaceable chuck.

12. The earth boring machine of claim 11 wherein said set of threads onthe rotary drill string is an external set of threads and the set ofthreads on the chuck is an internal set of threads.

13. The earth boring machine of claim 12 wherein said clamp ring meansis a clamp ring with a pair of flangesthat engage the main drive spindleand the replaceable chuck respectively.

14. The earth boring machine of claim 13 wherein the clamp ring isdivided into two semicircular ring elements that are connected by a pairof cap screws.

15. The earth boring machine of claim 13 wherein said clamp ringconsists of a pair of semicircular portions connected by a hinge and alock means.

16. The earth boring machine of claim 13 including floating means forallowing said replaceable chuck to float linearly relative to said maindrive spindle.

17. The earth boring machine of claim 16 including alignment means forproviding for alignment between the replaceable chuck and the main drivespindle.

18. The earth boring machine of claim 17 wherein said alignment meansincludes a register pilot extending from the repleaceable chuck and apilot recess in the main drive spindle.

1. An apparatus for transmitting rotary, compressive and tensile forcesto a drill string to drill a large diameter hole, comprising: rotarydrilling equipment including a main drive spindle, a motor for rotatingsaid main drive spindle and means for moving said main drive spindleaxially; first angular means on said main drive spindle for transmittingrotary force, said first angular means being a driving square recess inthe main drive spindle; a replaceable chuck including a connection forattaching the drill string; second angular means on said replaceablechuck that cooperate with said first angular means for transmittingrotary force, said second angular means being a driving squareprotruding from the replaceable chuck; and, clamp means connected to thereplaceable chuck and the main drive spindle for transmittingcompressive and tensile forces.
 2. The apparatus of claim 1 includingalignment means for providing alignment between the replaceable chuckand the main drive spindle.
 3. The apparatus of claim 2 wherein saidalignment means includes a register pilot extending from the replaceablechuck and a pilot recess in the main drive spindle.
 4. The apparatus ofclaim 3 wherein said connection for attaching the drill string includesa set of threads on the rotary drill string and a matching set ofthreads on the replaceable chuck.
 5. The apparatus of claim
 4. whereinsaid set of threads on the rotary drill string is an external set ofthreads and the set of threads on the replaceable chuck is an internalset of threads.
 6. The apparatus of claim 5 wherein said clamp means isa clamp ring with a pair of flanges that engage the main drive spindleand the replaceable chuck respectively.
 7. The apparatus of claim 6.wherein the clamp ring is divided into two semicircular ring elementsthat are connected by a pair of screws.
 8. The apparatus of claim 6.wherein said clamp ring consists of a pair of semicircular portionsconnected by a hinge and a lock means.
 9. The apparatus of claim 6.including floating means for allowing said replaceable chuck to floatlinearly relative to said main drive spindle.
 10. An earth boringmaching for drilling by the transmission of rotary and linear forces toa rotary drill string, comprising: rotary drilling equipment including amain drive spindle with first angular means for transmitting rotaryforces, said first angular means being a driving square recess in themain drive spindle; a replaceable chuck with means for connecting therotary drill string, said replaceable chuck having second angular meansfor transmitting rotary force that cooperate with said first angularmeans to transmit rotary force from said rotary drilling equipment tothe drill string, said second angular means being a driving squareprotruding from the replaceable chuck; and, clamp ring means connectedto the replaceable chuck and the main drive spindle for transmittinglinear force between the rotary drilling equipment and the drill string.11. The earth boring machine of claim 10 wherein said means forconnecting the rotary drill string to the rotary drilling equipmentincludes a set of threads on the rotary drill string and a matching setof threads on the replaceable chuck.
 12. The earth boring machine ofclaim 11 wherein said set of threads on the rotary drill string is anexternal set of threads and the set of threads on the chuck is aninternal set of threads.
 13. The earth boring machine of claim 12wherein said clamp ring means is a clamp ring with a pair of flangesthat engage the main drive spindle and the replaceable chuckrespectively.
 14. The earth boring machine of claim 13 wherein the clampring is divided into two semicircular ring elements that are connectedby a pair of cap screws.
 15. The earth boring machine of claim 13wherein said clamp ring consists of a pair of semicircular portionsconnected by a hinge and a lock means.
 16. The earth boring machine ofclaim 13 including floating means for allowing said replaceable chuck tofloat linearly relative to said main drive spindle.
 17. The earth boringmachine of claim 16 including alignment means for providing foralignment between the replaceable chuck and the main drive spindle. 18.The earth boring machine of claim 17 wherein said alignment meansincludes a register pilot extending from the replaceable chuck and apilot recess in the main drive spindle.